1. Field of the Technology:
The present invention relates to a piezoelectric driving apparatus, which drives a driven member in relation to a fixed member, by programmed applications of voltages across electrodes disposed on piezoelectric members.
2. Description of the Prior Art:
Hithereto, piezoelectric driving apparatus is known, for instance by a disclosure in Japanese Published examined Patent Application No. Sho 51-12497. The gist of this prior art is shown in FIG. 1. That is, the apparatus has a fixed member 4 and a moving member 23 which comprises a first end member 2 and a second member 3 which are slidably disposed on said fixed member 4. Between the first moving member 2 and the second moving member 3, a tubular piezoelectric member 1 is disposed, with their end parts fixed to the first end member 2 and the second end member 3, with coupling member such as bond layer on hard rubber couplers 12 and 13 inbetween, respectively. The tubular piezoelectric member 1 has electrodes 11 and 11' on its outside face and inside face, respectively, and a DC power source E.sub.1 is connected thereacross with a switch S.sub.1 inbetween. Across the first member 2 and fixed member 4, a second DC power source E2 is connected with a switch S.sub.2 inbetween. And across the second moving member 3 and the fixed member 4, a third DC power source E.sub.3 is connected with a switch S.sub.3 inbetween. The above-mentioned conventional apparatus makes the following operation: Firstly, switch S.sub.2 is closed, thereby fixing the first member 2 to the fixed member 4 by a DC absorption source. And then, by closing the switch S.sub.1, the piezoelectric element 1 is made to extend lengthwise, thereby moving the second moving member 3 rightward. Thereafter the switch S.sub.3 is closed thereby fixing the second moving member 3 to the fixed member 4 by electrostatic attractive force. Then the first switch S.sub.2 is open, thereby releasing the attraction of the first moving member 2. Then the switch S.sub.1 is open, thereby to restore the piezoelectric element 1 to its normal length. And thereafter, switch S.sub.2 is closed and the switch S.sub.3 is open. Thus, the moving member 23 is driven by one step rightwards in a motion like a measuring warm. And by repeating the same operation, step by step motion is available.
However, the above-mentioned apparatuses is using fixing means of electrostatic force type, and therefore its utility is limited. For instance, the above-mentioned electrostatic fixing means requires a special members, and also gives some outside influence due to large DC voltage for the absorption. Furthermore, the above-mentioned conventional apparatus comprises piezoelectric devices and two electrostatic fixing devices. And the electrostatic fixing devices have no relation with the piezoelectric motion. Accordingly, the above-mentioned operation like the measuring warm movement requires a specially controlled operations of the switches S1, S2 and S3 in a good timing relation, and therefore a considerable care must be taken. This is also a reason why the utility of the conventional apparatus is limited.